1. Field of the Invention
The present invention relates to a polyimide used for melt processing and more particularly relates to a polyimide having excellent processability and to a process for preparing the same.
2. Description of the Related Art
Polyimide obtained by reacting tetracarboxylic acid dianhydride with diamine has very high heat resistance and is additionally excellent in mechanical strength, dimensional stability, flame retardance and electrical insulation. Because of these preferred properties, polyimide has been conventionally used in various fields such as electric and electronic appliances, space and aeronautical equipment and transportation machinery. Thus, polyimide is a functional resin which is expected to be more widely used for fields where heat resistance is required. In view of the expanded fields of use, the required performance and application methods have been diversified and various polyimide resins having excellent properties to meet these requirements have been developed.
Some of these polyimide resins, however, have no distinct glass transition temperature, though excellent in heat resistance, and must be processed by such means as sinter molding in the case of using these resins as molding materials. Other kinds of polyimide are soluble in solvents such as halogenated hydrocarbons and have disadvantage in solvent resistance, though excellent in processability. Thus previously developed polyimides have both merits and drawbacks in the properties.